Activation of hexamethyldisilazane (HMDS) by TiO2 nanoparticles for protection of alcohols and phenols: the effect of the catalyst phase on catalytic activity
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Anatase TiO2 nanoparticles (TiO2 NPs) were synthesized by the sol–gel method using titanium tetra-isopropoxide (TTIP), isopropyl alcohol, and distilled water and then calcined at 400 °C for 3 h. X-ray diffraction and scanning electron microscopy methods, and Fourier transform infrared spectroscopy were used for characterization of the obtained TiO2 NPs. The obtained anatase TiO2 NPs were used as heterogeneous catalyst for trimethylsilation of various alcohols or phenols with hexamethyldisilazane (HMDS) in CH3CN at room temperature. High to quantitative yields of the products were obtained within short reaction times at room temperature using a very low loading of pure TiO2 NPs without any post-modification with Bronsted or Lewis acid species such as ClSO3H or HClO4. The catalyst can be recycled at least three times without significant loss of its activity. The results of this study provide evidence that the pure anatase phase of TiO2 exhibits higher catalytic activity in terms of catalyst loading and required reaction time compared to a mixture of anatase and rutile phases found in the commercial samples for trimethylsilation of various alcohols or phenols with HMDS.
KeywordsAnatase TiO2 Nano-catalyst Sol–gel Protection of alcohols Trimethylsilyl ethers Hexamethyldisilazane (HMDS)
We are grateful for the financial support from The Research Council of Iran University of Science and Technology (IUST), Tehran, Iran (Grant No. 160/771).
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